Phase Equilibria in the Au-Cu-In-Pd System at 500 °C and 800 °C: Experimental Study and Modeling

Phase equilibria in the Pd rich region of the Au-Cu-In-Pd quaternary at 500 °C and 800 °C are investigated by SEM, EDX and XRD techniques. Part of the isothermal tetrahedron was constructed accounting for published data for bounding ternaries obtained earlier by the present authors. No quaternary phases were detected. The solubility of copper in the τ₁ phase of the Au-In-Pd ternary (AuCu₃ structural type) does not exceed 5 at.%. Gold solubility in the InPd₂Cu phase of the Cu-In-Pd ternary is not less than 18 at.% at 500 °C, and at least 15 at.% at 800 °C. Analytical description of the boundaries of the FCC solid solutions in the equilibrium with the InPd₃, InPd₂Cu and ternary τ₁ phase was performed for bounding Cu-In-Pd and Au-In-Pd ternaries as well as for the quaternary. The tie-lines of the equilibria, i.e. the compositions of the two phases in equilibrium, were described as a single entity. To this end, the approach used in the literature for regression analysis of phase compositions of the (γ + γ′) Ni based superalloys was modified. The parametric descriptions of the two-phase tie-lines’ centers and those of the distribution coefficients of the components between the phases were built. The choice of parametrization is discussed. In particular cases of the ternaries and quaternary studied using the content of one or two of the components as parameters proved to be quite satisfactory. Very good description of the solubility lines and solubility surface including rather fine details has been achieved.Please check and confirm the edit made in the article title.Ok